Like most wildlife species, African Lions have evolved not to show stress or weakness until it becomes severe. In some species it is possible to determine stress levels by assessing adrenal activity over a period of time. This is done in humans by taking blood and assaying for corticosteroids, but this is clearly not an option for lions. We have often determined the reproductive status of females by examining the estrogen and progesterone metabolites in fecal samples collected on a regular basis. We have now applied the same technology to develop a corticosteroid assay specifically for lions. We are now pairing corticosteroid measures with observed behavioural assessments to determine behavioural indices of adrenal activity in this species.